Method of forming a metal or metal nitride interface layer between silicon nitride and copper

ABSTRACT

A method of forming a metal or metal nitride layer interface between a copper layer and a silicon nitride layer can include providing a metal organic gas or metal/metal nitride precursor over a copper layer, forming a metal or metal nitride layer from reactions between the metal organic gas or metal/metal nitride precursor and the copper layer, and depositing a silicon nitride layer over the metal or metal nitride layer and copper layer. The metal or metal nitride layer can provide a better interface adhesion between the silicon nitride layer and the copper layer. The metal layer can improve the interface between the copper layer and the silicon nitride layer, improving electromigration reliability and, thus, integrated circuit device performance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.10/145,944, entitled METHOD OF FORMING AN ADHESION LAYER WITH AN ELEMENTREACTIVE WITH A BARRIER LAYER, filed on an even date herewith byLopatin, et al. and assigned to the same assignee as this application.

FIELD OF THE INVENTION

The present invention relates generally to integrated circuits andmethods of manufacturing integrated circuits. More particularly, thepresent invention relates to forming a metal interface layer betweensilicon nitride and copper.

BACKGROUND OF THE INVENTION

In general, as semiconductor devices or integrated circuits have becomesmaller, the corresponding current densities across the metal conductorsin the devices have increased. Metal conductors typically have an uppercurrent density limit imposed by the phenomenon of electromigration. Forexample, aluminum conductors experience electromigration problems atcurrent densities of approximately 10⁵ amperes per square centimeter(A/cm²).

Electromigration refers to the transport of mass in metals due to theelectric current. Electromigration is caused by the transfer of momentumfrom the electrons associated with the electric current to the positivemetal ions. When a significant amount of current passes through thinmetal conductors in semiconductor devices or integrated circuits, themetal ions associated with thin metal conductors are transported andtend to accumulate in some regions and be removed from other regions.The accumulation or pileup of the metal ions can short circuit adjacentconductors in the device. The removal of metal ions in other regions maycreate voids which result in an open circuit. Short circuits and opencircuits caused by electromigration often result in device failure.

Electromigration failures have been described by Stanley Wolf, Ph.D. inSilicon Processing for the VLSI Era, Lattice Press, Sunset Beach,Calif., Vol. 2, pp. 264-65 (1990). Dr. Wolf explains that a positivedivergence of the motion of the ions of a conductor leads to anaccumulation of vacancies, forming a void in the metal. Such voids mayultimately grow to a size that results in open-circuit failure of theconductor line.

Integrated circuits typically include multiple layers of conductivelines separated by dielectric layers. These layers of conductive linesare typically referred to as metal layers (e.g., metal 1, metal 2, metal3, etc.) and the dielectric layers are typically referred to asinterlevel dielectric layers (ILD0, ILD1, ILD2, etc.). Copper linedfilms are being considered for use in metal layers due to theirresistivity and resistance to electromigration.

Conductive lines and metal layers are discussed in U.S. Pat. Nos.5,646,448; 5,770,519; and 5,639,691; each of which are assigned to theassignee of the present application. Generally, barrier layers areutilized with copper containing conductive structures to prevent copperdiffusion into silicon substrates and insulative layers. Copperdiffusion into silicon substrate degrades device integrity (“poison” thedevice) as well as the copper structure. Similarly, copper diffusioninto insulative structures degrades performance of the insulativelayers, as well as the copper structure.

Conventionally, barrier layers, such as silicon nitride have beenutilized between the copper structure and the substrate and insulativelayer. However, the interface between the silicon nitride material andthe copper structure can be poor if the silicon nitride material is notprocessed properly. For example, chemical vapor deposited (CVD) siliconnitride must be pre-treated to ensure a proper interface. CVD siliconnitride without pre-treatment results in a poor Cu/SiN interface andpossible delamination of the copper from the silicon nitride.Delamination creates a path from which copper ions can diffuse outwardand to which moisture and other contaminates can diffuse inward. U.S.Pat. No. 6,271,595 discusses compounds which can be applied to coppersurfaces to increase adhesion between copper and silicon nitride.

Thus, there is a need for an improved interface adhesion between siliconnitride and copper. Further, there is a need for a method of forming ametal interface layer between silicon nitride and copper. Even further,there is a need for a method of adding a metal organic precursor beforesilicon nitride chemical vapor deposition (CVD) to improve the siliconnitride interface.

SUMMARY OF THE INVENTION

An exemplary embodiment is related to a method of forming a metal layerinterface between a copper layer and a silicon nitride layer. Thismethod can include providing a metal organic gas over a copper layer,forming a metal layer from reactions between the metal organic gas andthe copper layer, and depositing a silicon nitride layer over the metallayer and copper layer. The metal layer can provide an interfaceadhesion between the silicon nitride layer and the copper layer.

Another exemplary embodiment is related to a method of improving asilicon nitride and copper interface using added elements. The methodcan include providing a copper layer over an integrated circuitsubstrate, depositing added elements in a metal organic gas over thecopper layer where the added elements react to copper in the copperlayer and form a metal layer on top of the copper layer, and depositingsilicon nitride over the metal layer and copper layer.

Another exemplary embodiment is related to a method of forming a via inan integrated circuit. This method can include depositing a copperlayer, depositing an etch stop layer over the copper layer, depositingan insulating layer over the etch stop layer, forming an aperture in theinsulating layer and the etch stop layer, depositing added elements in ametal organic gas over the copper layer where the added elements reactto copper in the copper layer to form a metal layer on top of the copperlayer, and depositing silicon nitride over the metal layer and copperlayer.

Other principle features and advantages of the invention will becomeapparent to those skilled in the art upon review of the followingdrawings, the detailed description, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The exemplary embodiments will hereafter be described with reference tothe accompanying drawings, wherein like numerals denote like elements,and:

FIG. 1 is a schematic cross-sectional view representation of a portionof an integrated circuit, showing metal organic gas provided over acopper layer; and

FIG. 2 is a schematic cross-sectional view representation of a portionof an integrated circuit, showing a metal layer intermediate siliconnitride and copper.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

With reference to FIG. 1, a schematic cross-sectional viewrepresentation of a portion 100 of an integrated circuit (IC) includes ametal layer 132. Metal layer 132 can be a metal 1 layer, a metal 2 layeror any interconnect layer used in an integrated circuit. Metal layer 132includes a copper interconnect layer, or line 110, an interleveldielectric (ILD) material 120, an interlevel dielectric (ILD) material130, and a barrier structure 128. Metal layer 132 can be provided abovean interlevel dielectric layer 131. Layer 131 can correspond to an ILDlayer 0, an ILD layer 1, or any insulative layer used in an integratedcircuit.

Layer 131 is preferably a 2000 to 7000 Angstroms thick (TEOS) depositedsilicon oxide layer. Alternatively, layer 131 can be a low-k dielectricmaterial. Portion 100 is preferably part of an ultra-large-scaleintegrated (ULSI) circuit having millions or more transistors. Portion100 is manufactured as part of the integrated circuit on a semiconductorwafer, such as, a silicon wafer.

Copper line 110 can be a layer including copper or a copper alloy.Copper line 110 can be deposited by ECP, CVD or PVD and formed accordingto a damascene technique. In an exemplary embodiment, copper line 110has a thickness of 2000 to 7000 Angstroms. Interlevel dielectricmaterials 120 and 130 can include dielectric materials, such as oxide ornitride. Interlevel dielectric materials 120 and 130 can be deposited byCVD or spin-on and have a thickness of 2000 to 7000 Angstroms.

Copper line 110 is preferably provided in a U-shaped barrier structure128. Barrier structure 128 is preferably a 40 to 400 Angstroms thicklayer of titanium or tantalum deposited by PVD or CVD. Alternatively,structure 128 can be TiN, TaN, W, WN or other Cu barrier metals.Moreover, barrier structure 128 can also include any dielectric Cubarrier materials, such as SiC or SiN deposited by PVD or CVD.

After copper line 110 is formed and is situated between materials 120and 130, a metal organic gas or metal/metal nitride deposition gas 140can be provided to a surface 150 of portion 100. Preferably, metalorganic gas or metal/metal nitride deposition gas 140 can includeprecursors elements, such as Ta, W, Mo, Cr, Zr, Mn, Co, Ni, Ag, Au, Sn,Mg, Ca, Ba, Al, Ti, Sr, or Cu. Metal organic gas or metal/metal nitridedeposition 140 can be provided before a chemical vapor deposition (CVD)of silicon nitride (SiN). In an exemplary embodiment, metal organic gasor metal/metal nitride deposition 140 is provided as a vapor in a vacuumchamber 400 degrees Celsius. The time for this process can be from 1 to100 seconds at a temperature from 200 to 700° C. This process ispreferably done in the same process chamber as the subsequent SiNdeposition (in-situ). However, it can also be done in other CVD or PVDchambers (ex-situ). A plasma power can be applied to enhance chemicalreaction for the metal organic gas or metal/metal nitride depositiongases with surface 150 or with other process gasses (e.g., H, N, NH3).In an exemplary embodiment, the plasma can be a 13.56 MHz RF source with0 to 500 W power, with or without Ar or He.

Depending on the precursor, the gas flow rate can be in the range of 5to 1000 sccm. By the way of example, precursor dimethylethylamine alanecan be used for Al deposition. Also as examples, precursors such as Cu l(tmvs) (hfac), described in Proceedings of IEEE InternationalReliability Physics Symposium 1997, pp. 201-205, or a CupraSelectprecursor can be used in the above process to form a thin Cu layer witha better adhesion to the SiN (in-situ). A precursor, such astetrakis(diethylamino)titanium (TDEAT) andtetrakis(dimethylamino)titanium (TDMAT), can be used to form Ti or TiNlayer. Other metal nitride precursors include, by way of example,Tris(dimethylamino)alane for AIN, Tris(dimethylamino)borane for BN,Tetrakis(diethylamino)tin for SnN, Tetrakis(diethylamino)zirconium andTetrakis(dimethylamino)zirconium for ZrN, etc. Other possible precursorsinclude SiH4, GeH4, AlH3(NMe3)2, NH3, PH3, TiCl4, TaCl5, MoF6, WF6,SiHMe3, AlMe3, AliBu3, Ti(CH2tBu)4, Ti(NMe2)4, Cr(NEt2)4, Cu(acac)2,Pt(hfac)2 etc.

Metal organic gas or metal/metal nitride deposition gas 140 can includeprecursor elements that react with surface 150 of copper line 110 toform a thin metal or metal nitride layer 160 (FIG. 2) or 140 to reactwith other process gasses (H, N, NH3 for examples) to deposit a thinmetal or metal nitride layer 160 on 150. Preferred precursor elementsinclude Ta, TaN, Ti, TiN, W, WN. However, precursor elements could alsoinclude, Mo, Cr, Zr, Mn, Co, Ni, Ag, Au, Sn, Mg, Ca, Ba, Al, Sr, or Cuor their nitrides. By way of example, thin metal or metal nitride layer160 can be 10 to 100 Angstroms thick. The metal or metal nitride layercan improve the interface adhesion between copper line 110 and siliconnitride layer 170 (FIG. 2), and therefore improving Cu line electricaland electromigration performances.

FIG. 2 illustrates portion 100 described with reference to FIG. 1 withthe addition of a thin metal layer 160 on copper line 110 and a siliconnitride layer 170 over thin metal layer 160. In an exemplary embodiment,silicon nitride layer 170 can have a thickness of 200 to 700 Angstromsand is deposited by PE-CVD. After silicon nitride layer 170 is provided,an insulative layer similar to layer 131 can be provided over layer 170.

Advantageously, thin metal layer 160 improves the interface betweencopper layer 110 and silicon nitride layer 170. Further, thin metallayer 160 improves electromigration reliability and, thus, integratedcircuit device performance.

While the exemplary embodiments illustrated in the FIGURES and describedabove are presently preferred, it should be understood that theseembodiments are offered by way of example only. Other embodiments mayinclude, for example, different precursor elements and different methodsof forming a thin metal layer on a copper layer. The invention is notlimited to a particular embodiment, but extends to variousmodifications, combinations, and permutations that nevertheless fallwithin the scope and spirit of the appended claims.

What is claimed is:
 1. A method of forming a metal layer interfacebetween a copper layer and a silicon nitride layer, the methodcomprising: providing a metal organic gas over a copper layer; forming ametal layer from reactions between the metal organic gas and the copperlayer; and depositing a silicon nitride layer over the metal layer andcopper layer, the metal layer providing an interface adhesion betweenthe silicon nitride layer and the copper layer.
 2. The method of claim1, wherein the metal organic gas includes metal organic precursorelements.
 3. The method of claim 1, wherein the metal organic precursorelements include magnesium (Mg), calcium (Ca), barium (Ba), aluminum(Al), titanium (Ti), or strontium (Sr).
 4. The method of claim 1,wherein the metal layer is a metal nitride layer.
 5. The method of claim1, wherein forming a metal layer includes annealing the copper layer at400° C.
 6. The method of claim 1, wherein providing a metal organic gasover a copper layer is done in a vacuum chamber.
 7. The method of claim1, wherein depositing a silicon nitride layer over the metal layer andcopper layer includes performing a chemical vapor deposition (CVD) ofsilicon nitride.
 8. The method of claim 1, wherein the metal layerincludes Al, Cu, Ag, Au.
 9. A method of improving a silicon nitride andcopper interface using added elements, the method comprising: providinga copper layer over an integrated circuit substrate; depositing addedelements in a metal organic gas over the copper layer, the addedelements reacting to copper in the copper layer to form a metal layer ontop of the copper layer; and depositing silicon nitride over the metallayer and copper layer.
 10. The method of claim 9, wherein the metallayer has a thickness of approximately 10 Angstroms.
 11. The method ofclaim 9, wherein the added elements include magnesium (Mg), calcium(Ca), barium (Ba), aluminum (Al), titanium (Ti), or strontium (Sr). 12.The method of claim 9, wherein the metal organic gas is a metal nitrideprecusor.
 13. The method of claim 9, wherein the silicon nitride is avia.
 14. The method of claim 9, further comprising annealing the copperlayer to form the metal layer.
 15. A method of forming a via in anintegrated circuit, the method comprising: depositing a copper layer;depositing an etch stop layer over the copper layer; depositing aninsulating layer over the etch stop layer; forming an aperture in theinsulating layer and the etch stop layer; depositing added elements in ametal organic gas over the copper layer, the added elements reacting tocopper in the copper layer to form a metal layer on top of the copperlayer; and depositing silicon nitride over the metal layer and copperlayer.
 16. The method of claim 15, wherein the metal layer has athickness of approximately 10 Angstroms.
 17. The method of claim 15,wherein the added elements include magnesium (Mg), calcium (Ca), barium(Ba), aluminum (Al), titanium (Ti), orstrontium (Sr).
 18. The method ofclaim 15, wherein depositing added elements in a metal organic gas overthe copper layer is done in a vacuum chamber.
 19. The method of claim15, wherein depositing silicon nitride over the metal layer and copperlayer includes performing a chemical vapor deposition (CVD) of siliconnitride.
 20. The method of claim 15, wherein the metal organic gas is ametal nitride precursor and the metal layer is a metal nitride layer.